Armed Bear Common Lisp (ABCL) is an implementation of ANSI Common Lisp that runs in a Java virtual machine. It provides a runtime system, a compiler that compiles Lisp source to JVM bytecode, and an interactive REPL for program development.

ABCL is distributed under the terms of the GNU General Public License, with a special linking exception - known as Classpath exception. If you link ABCL with your own program, then you do not need to release the source code for that program. However, any changes that you make to ABCL itself must be released in accordance with the terms of the GPL.